main(){
  Person person = Person();
  print(person.name);
  print(person.age);
  print(person.height);
  print(person.isStudent);
  person.sayHello();
}

//定义一个Person类
class Person {
  String name = "张三";
  int age = 18;
  double height = 1.80;
  bool isStudent = true;

  void sayHello() {
    print("Hello, My name is $name, I am $age years old, I am $height meters tall, and I am a student: $isStudent");
  }
}